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Abstract:

A camera device (1) includes: an imaging unit (2) having a complementary
color filter; a color temperature estimating unit (8) that estimates a
color temperature on the basis of a video signal obtained from the
imaging unit (2); a color parameter calculating unit (9) that calculates
a color parameter value corresponding to the estimated color temperature;
and a color calibrating unit (7) that performs color calibration using
the calculated color parameter value. The color parameter calculating
unit (9) calculates the color parameter value corresponding to the
estimated color temperature on the basis of color parameter values (a
first color parameter value and a second color parameter value) at two
reference color temperatures (a first color temperature 2000 K and a
second color temperature 3200 K). This allows performing color
calibration with high color reproducibility using suitable color
parameter values according to a change in an illumination condition as
well as allows substantially reducing an amount of data required to
determine the suitable color parameter values.

Claims:

1. A camera device comprising: an imaging unit; a color temperature
estimating unit that estimates a color temperature on the basis of a
video signal obtained from the imaging unit; a color parameter
calculating unit that calculates a color parameter value corresponding to
the estimated color temperature on the basis of a first color parameter
value and a second color parameter value being color parameter values at
a first color temperature and a second color temperature being two
reference color temperatures; and a color calibrating unit that performs
color calibration using the calculated color parameter value.

2. The camera device according to claim 1, further comprising a color
parameter controlling unit that gradually changes a color parameter value
used for the color calibration from a color parameter value corresponding
to a standard color temperature to the calculated color parameter value.

3. The camera device according to claim 1, further comprising: a movement
detecting unit that detects a moving object in an image captured by the
imaging unit; and a second color parameter controlling unit that
suppresses, when the moving object is detected, changing of a color
parameter value used for the color calibration from a color parameter
value corresponding to a standard color temperature to the calculated
color parameter value.

4. The camera device according to claim 1, further comprising a
determining unit that determines, on the basis of a degree of
relationship between the estimated color temperature and a current time,
whether or not the calculated color parameter value is used for the color
calibration.

5. A color calibrating method used in a camera device including an
imaging unit, the method comprising: estimating a color temperature on
the basis of a video signal obtained from the imaging unit; calculating a
color parameter value corresponding to the estimated color temperature on
the basis of a first color parameter value and a second color parameter
value being color parameter values at a first color temperature and a
second color temperature being two reference color temperatures; and
performing color calibration using the calculated color parameter value.

6. A program for color calibration performed by a camera device, the
program causing a computer to execute: processing for estimating a color
temperature on the basis of a video signal obtained from an imaging unit
of the camera device; processing for calculating a color parameter value
corresponding to the estimated color temperature on the basis of a first
color parameter value and a second color parameter value being color
parameter values at a first color temperature and a second color
temperature being two reference color temperatures; and processing for
performing color calibration using the calculated color parameter value.

Description:

[0002] Conventionally, a camera device such as a surveillance camera has
used a complementary color CCD (an image pickup device having a
complementary color filter) in order to increase the sensitivity of the
camera. In such a conventional camera device, color parameters are set
according to the spectral sensitivities of the complementary color CCD,
and color calibration (calibration) is performed using the color
parameters (e.g., see Patent Literature 1). The values of the color
parameters are usually set according to illumination conditions of
so-called standard light sources (e.g., a color temperature 3200 K).

[0003] However, in the conventional camera devices, because color
parameter values are set according to illumination conditions of standard
light sources (e.g., a halogen light of a color temperature 3200 K), if
an illumination condition is changed, a color phase shift occurs and
suitable color calibration is not performed. For example, if a color
temperature of a light source is extremely low (especially, under an
illumination condition close to a near-infrared light such as
illumination in tunnels), although an actual color is whitish, suitable
color calibration is not performed, resulting in an orangish color.

[0004] Thus, it is contemplated to calibrate a difference of a color
parameter by using a technique that specifies any color parameter value
in a three-dimensional color space (a color space of luminance in one
dimension and chrominance in two dimensions). However, there are
innumerable color parameters based on primary colors and complementary
colors (e.g., three primary colors of "R," "G," and "B" and three
complementary colors of "Cy," "Mg," and "Ye") as well as a calibration
amount for a color parameter is different for each color temperature.
Therefore, since a data amount of a table storing calibration amounts for
all color parameters for each color temperature would be enormous, it is
difficult to say that this table is practical.

CITATION LIST

Patent Literature

[0005] Patent Literature 1: Japanese Patent Laid-Open No. 2008-104046

SUMMARY OF INVENTION

Technical Problem

[0006] The present invention has been made in view of such circumstances.
An object of the present invention is to provide a camera device that can
perform color calibration with high color reproducibility using suitable
color parameter values according to a change in an illumination condition
as well as can substantially reduce an amount of data required to
determine the suitable color parameter values.

Solution to Problem

[0007] An aspect of the present invention is a camera device. The camera
device includes: an imaging unit; a color temperature estimating unit
that estimates a color temperature on the basis of a video signal
obtained from the imaging unit; a color parameter calculating unit that
calculates a color parameter value corresponding to the estimated color
temperature on the basis of a first color parameter value and a second
color parameter value being color parameter values at a first color
temperature and a second color temperature being two reference color
temperatures; and a color calibrating unit that performs color
calibration using the calculated color parameter value.

[0008] Another aspect of the present invention is a color calibrating
method. The color calibrating method is used in a camera device including
an imaging unit and includes: estimating a color temperature on the basis
of a video signal obtained from the imaging unit; calculating a color
parameter value corresponding to the estimated color temperature on the
basis of a first color parameter value and a second color parameter value
being color parameter values at a first color temperature and a second
color temperature being two reference color temperatures; and performing
color calibration using the calculated color parameter value.

[0009] Yet another aspect of the present invention is a program for color
calibration performed by a camera device. The program causes a computer
to execute: processing for estimating a color temperature on the basis of
a video signal obtained from an imaging unit of the camera device;
processing for calculating a color parameter value corresponding to the
estimated color temperature on the basis of a first color parameter value
and a second color parameter value being color parameter values at a
first color temperature and a second color temperature being two
reference color temperatures; and processing for performing color
calibration using the calculated color parameter value.

[0010] As described later, there are other aspects of the present
invention. Therefore, the disclosure of this invention is intended to
provide some aspects of the present invention, and is not intended to
limit the scope of the invention described herein and claimed.

BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 is a block diagram illustrating a configuration of a camera
device according to an embodiment of the present invention.

[0013]FIG. 3 is a flow diagram illustrating a flow of basic color
calibration processing in the embodiment of the present invention.

[0014]FIG. 4 is a flow diagram illustrating a flow of color calibration
processing performed when movement detection is carried out.

[0015] FIG. 5 is a flow diagram illustrating a flow of color calibration
processing performed when a degree of relationship between a color
temperature and a current time is determined.

DESCRIPTION OF EMBODIMENT

[0016] Detailed description of the present invention will be made below.
However, the following detailed description and the accompanying drawings
do not limit the invention.

[0017] A camera device of the present invention has a configuration
including: an imaging unit; a color temperature estimating unit that
estimates a color temperature on the basis of a video signal obtained
from the imaging unit; a color parameter calculating unit that calculates
a color parameter value corresponding to the estimated color temperature
on the basis of a first color parameter value and a second color
parameter value being color parameter values at a first color temperature
and a second color temperature being two reference color temperatures;
and a color calibrating unit that performs color calibration using the
calculated color parameter value.

[0018] This configuration allows calculating a color parameter value
corresponding to a color temperature estimated from a video signal with
only data of color parameter values (a first color parameter value and a
second color parameter value) at two reference color temperatures (a
first color temperature and a second color temperature). An amount of the
data of the first color parameter value and the second color parameter
value is much smaller than an amount of data required for conventional
color parameter calibration. This allows performing color calibration
with high color reproducibility using suitable color parameter values
according to a change in an illumination condition as well as allows
substantially reducing an amount of data required to determine the
suitable color parameter values.

[0019] Further, the camera device of the present invention may have a
configuration including a color parameter controlling unit that gradually
changes a color parameter value used for the color calibration from a
color parameter value corresponding to a standard color temperature to
the calculated color parameter value.

[0020] According to the configuration, when color calibration is performed
using the color parameter value calculated in accordance with a change in
an illumination condition, a color parameter value is controlled so as to
be gradually changed from a color parameter value corresponding to a
standard color temperature. This prevents sharp color calibration from
occurring when an illumination condition is changed, and color
calibration (color calibration using suitable color parameter values) is
performed naturally and gradually.

[0021] Further, the camera device of the present invention may have a
configuration including: a movement detecting unit that detects a moving
object in an image captured by the imaging unit; and a second color
parameter controlling unit that suppresses, when the moving object is
detected, changing from a color parameter value corresponding to a
standard color temperature to the calculated color parameter value.

[0022] According to the configuration, if a captured image includes a
moving object, a color temperature may be erroneously estimated, but in
such a case, a color parameter value is controlled so that color
calibration is performed using a color parameter value corresponding to a
standard color temperature. This allows preventing color calibration
using a color parameter value calculated on the basis of an erroneously
estimated color temperature (an unsuitable color parameter value).

[0023] Further, the camera device of the present invention may have a
configuration including a determining unit that determines, on the basis
of a degree of relationship between the estimated color temperature and a
current time, whether or not the calculated color parameter value is used
for the color calibration.

[0024] According to the configuration, if a degree of relationship between
a color temperature estimated from a video signal and a current time is
low, a color temperature may be erroneously estimated, but in such a
case, it is determined that the calculated color parameter value is not
used for the color calibration (i.e., the color calibration is performed
using a color parameter value corresponding to a standard color
temperature). This allows preventing color calibration using a color
parameter value calculated on the basis of an erroneously estimated color
temperature (an unsuitable color parameter value).

[0025] A color calibrating method of the present invention is a color
calibrating method used in a camera device including an imaging unit and
includes: estimating a color temperature on the basis of a video signal
obtained from the imaging unit; calculating a color parameter value
corresponding to the estimated color temperature on the basis of a first
color parameter value and a second color parameter value being color
parameter values at a first color temperature and a second color
temperature being two reference color temperatures; and performing color
calibration using the calculated color parameter value.

[0026] As before, the method also allows calculating a color parameter
value corresponding to a color temperature estimated from a video signal
with only data of color parameter values (a first color parameter value
and a second color parameter value) at two reference color temperatures
(a first color temperature and a second color temperature). Therefore,
color calibration with high color reproducibility can be performed using
suitable color parameter values according to a change in an illumination
condition as well as an amount of data required to determine the suitable
color parameter values can be substantially reduced.

[0027] A program of the present invention is a program for color
calibration performed by a camera device and causes a computer to
execute: processing for estimating a color temperature on the basis of a
video signal obtained from an imaging unit of the camera device;
processing for calculating a color parameter value corresponding to the
estimated color temperature on the basis of a first color parameter value
and a second color parameter value being color parameter values at a
first color temperature and a second color temperature being two
reference color temperatures; and processing for performing color
calibration using the calculated color parameter value.

[0028] As before, the program also allows calculating a color parameter
value corresponding to a color temperature estimated from a video signal
with only data of color parameter values (a first color parameter value
and a second color parameter value) at two reference color temperatures
(a first color temperature and a second color temperature). Therefore,
color calibration with high color reproducibility can be performed using
suitable color parameter values according to a change in an illumination
condition as well as an amount of data required to determine the suitable
color parameter values can be substantially reduced.

[0029] The present invention includes the color parameter calculating unit
that calculates a color parameter value used for color calibration on the
basis of color parameter values at two reference color temperatures,
thereby allowing performing color calibration with high color
reproducibility using suitable color parameter values according to a
change in an illumination condition as well as allowing substantially
reducing an amount of data required to determine the suitable color
parameter values.

[0030] Now, the camera device according to the embodiment of the present
invention will be described below using the drawings. The present
embodiment illustrates a case of a camera device used as a surveillance
camera and the like. This camera device includes a color calibration
function. This function is implemented by a program stored in memory or
the like of the camera device.

[0031] The configuration of the camera device according to the embodiment
of the present invention will be described with reference to the
drawings. FIG. 1 is a block diagram illustrating the configuration of the
camera device according to the present embodiment. As illustrated in FIG.
1, the camera device 1 includes an imaging unit 2 including a
complementary color CCD (an image pickup device having a complementary
color filter), a video processing unit 3 composed of a DSP or the like,
and a microcomputer 4 that controls an operation of the video processing
unit 3.

[0032] The video processing unit 3 includes a white detecting unit 5 that
detects a white color area (a white area) included in an image captured
by the imaging unit 2, a movement detecting unit 6 that detects a moving
object included in an image captured by the imaging unit 2, and a color
calibrating unit 7 that performs color calibration using a calculated
color parameter value (described later).

[0033] On the other hand, the microcomputer 4 includes a color temperature
estimating unit 8 that estimates a color temperature on the basis of a
video signal of a white area detected by the white detecting unit 5, a
color parameter calculating unit 9 that calculates a color parameter
value corresponding to the estimated color temperature, and a color
parameter controlling unit 10 that controls the color parameter value
used for the color calibration.

[0034] Furthermore, the microcomputer 4 includes a clock unit 11 that can
obtain current time information, and a determining unit 12 that
determines, on the basis of a degree of relationship between the
estimated color temperature and a current time, whether or not the color
parameter value calculated by the color parameter calculating unit 9 is
used for color calibration.

[0035] The color parameter calculating unit 9 has a function to calculate
a color parameter value corresponding to the estimated color temperature
on the basis of color parameter values (a first color parameter value and
a second color parameter value) at two reference color temperatures (a
first color temperature and a second color temperature). The first color
temperature is 2000 K, for example. The second color temperature is 3200
K, for example.

[0036] Now, the function of the color parameter calculating unit 9 will be
described in detail with reference to FIG. 2. FIG. 2 is a diagram
explaining processing in the color parameter calculating unit 9
(processing for calculating a color conversion rate). FIG. 2 illustrates
the case of calculating color parameter values of "R" and "B" using color
conversion rates.

[0037] First, processing for calculating a color parameter value of "B"
will be described. As illustrated in FIG. 2, the color parameter
calculating unit 9 holds color parameter values (shown by white circles)
of "B" at premeasured two reference color temperatures (2000 K and 3200
K) as two reference color conversion rates (0% and 100%). The color
conversion rate indicates a percentage (%) in which a value to be
calculated as a color parameter value corresponding to an estimated color
temperature is changed from the value of one color temperature (2000 K)
to the value of the other color temperature (3200 K), with color
parameter values of "B" at the two color temperatures (2000 K and 3200 K)
as a reference.

[0038] For example, if the color conversion rate is 0%, a color parameter
value of "B" at the color temperature 2000 K is calculated as the color
parameter value corresponding to the estimated color temperature. In this
case, the value has not been changed at all from the value of the color
temperature 2000 K to the value of the color temperature 3200 K (i.e.,
the color conversion rate is 0%).

[0039] On the other hand, if the color conversion rate is 100%, a color
parameter value of "B" at the color temperature 3200 K is calculated as
the color parameter value corresponding to the estimated color
temperature. In this case, the value has been completely changed from the
value of the color temperature 2000 K to the value of the color
temperature 3200 K (i.e., the color conversion rate is 100%).

[0040] The color parameter calculating unit 9 calculates a color parameter
value corresponding to an estimated color temperature using such a color
conversion rate curve. For example, assume that the estimated color
temperature is 3000 K. In this case, as illustrated in FIG. 2, the color
conversion rate curve indicates that a color conversion rate of "B" is
"80%," and a value obtained by changing the value of the color
temperature 2000 K to the value of the color temperature 3200 K by "80%"
is calculated as a color parameter value of "B" corresponding to the
estimated color temperature (3000 K).

[0041] Note that a description will be omitted here, but color parameter
values corresponding to an estimated color temperature (e.g., 3000 K) are
similarly calculated for other colors such as "R." For example, for "R,"
as illustrated in FIG. 2, a value obtained by changing the value of the
color temperature 3200 K to the value of the color temperature 2000 K by
"10%" is calculated as a color parameter value of "R" corresponding to
the estimated color temperature (3000 K).

[0042] It should be noted that the foregoing has described the example in
which with the color parameter values at the two reference color
temperatures (2000 K and 3200 K) as a reference, the rates of change
(color conversion rates) from the values at one color temperature (2000
K) to the values at the other color temperature (3200 K) are approximated
by the "curves," but the scope of the present invention is not limited
thereto. For example, the color conversion rates may be approximated by
"straight lines." In addition, the two reference color temperatures are
not limited to 2000 K and 3200 K.

[0043] Next, a function of the color parameter controlling unit 10 will be
described. The color parameter controlling unit 10 has a function to
gradually (e.g., slowly in five seconds) change a color parameter value
used for color calibration from a color parameter value corresponding to
a standard color temperature (simply also referred to as the "standard
value") to a color parameter value calculated by the color parameter
calculating unit 9 (simply also referred to as the "calculated value").
The standard color temperature is 3200 K, for example.

[0044] Furthermore, the color parameter controlling unit 10 has a function
to, if the movement detecting unit 6 detects a moving object, suppress
changing of a color parameter value used for color calibration from a
standard value to a calculated value. Therefore, the color parameter
controlling unit 10 acts also as the second color parameter controlling
unit 10 of the present invention. It should be noted that the processing
for suppressing changing from a standard value to a calculated value
includes processing for preventing changing from a standard value to a
calculated value (allowing no changing) and processing for reducing an
amount of change from a standard value to a calculated value (allowing
slight changing).

[0045] Next, a function of the determining unit 12 will be described. If a
degree of relationship between an estimated color temperature and a
current time is low, the determining unit 12 determines that the color
parameter value calculated by the color parameter calculating unit 9 is
not used for the color calibration. For example, if an estimated color
temperature is low (e.g., under an illumination condition of an orange
color), when a current time is "morning" or "daytime," the determining
unit 12 determines that a degree of relationship between the color
temperature and the current time is low. If the determining unit 12
determines that a degree of relationship between a color temperature and
a current time is low, the color parameter controlling unit 10 suppresses
changing of a color parameter value used for the color calibration from
the standard value to the calculated value in the same manner as
described above.

[0046] An operation of the camera device 1 configured as described above
will be described with reference to the drawings. Here, the following
description will focus on a flow of color calibration processing being a
feature of the present invention.

[0047]FIG. 3 is a flow diagram illustrating a flow of basic color
calibration processing in the embodiment of the present invention. As
illustrated in FIG. 3, in the basic color calibration processing, first,
the imaging unit 2 captures an image (S1), then the white detecting unit
5 detects a white area in the image (S2), and the color temperature
estimating unit 8 estimates a color temperature from the white area (S3).
Then, the color parameter calculating unit 9 calculates a color parameter
value from the estimated color temperature using a color conversion rate
as described above (S4). The parameter controlling unit gradually changes
a color parameter value used for color calibration from a standard value
to the calculated value (S5), and the color calibrating unit 7 performs
color calibration processing using the color parameter value (S6).

[0048]FIG. 4 is a flow diagram illustrating a flow of color calibration
processing performed when movement detection is carried out. In this
case, as illustrated in FIG. 4, first the imaging unit 2 captures an
image (S1), and then the movement detecting unit 6 detects whether or not
the image includes a moving object (S7). If the moving object is detected
in the image, the parameter controlling unit performs controlling to
suppress changing of a color parameter value used for color calibration
from a standard value to a calculated value (S8), and the color
calibrating unit 7 performs color calibration processing using the color
parameter value (S9). If any moving object is not detected in the image,
the same processing (S2 to S6) as that of the basic color calibration
processing is performed.

[0049] FIG. 5 is a flow diagram illustrating a flow of color calibration
processing performed when a degree of relationship between a color
temperature and a current time is determined. In this case, as
illustrated in FIG. 5, like the basic color calibration processing, first
the imaging unit 2 captures an image (S1), then the white detecting unit
5 detects a white area in the image (S2), and the color temperature
estimating unit 8 performs processing to estimate a color temperature
from the white area (S3). Then, the determining unit 12 determines
whether or not the estimated color temperature is associated with a
current time (whether a degree of relationship is high or not) (S10). If
it is determined that the degree of relationship between the color
temperature and the current time is low, the parameter controlling unit
performs controlling to suppress changing of a color parameter value used
for color calibration from a standard value to a calculated value (S11),
and the color calibrating unit 7 performs the color calibration
processing using the color parameter value (S12). If it is determined
that the degree of relationship between the color temperature and the
current time is high, the same processing (S4 to S6) as that of the basic
color calibration processing is performed.

[0050] The camera device 1 according to the embodiment of the present
invention includes the color parameter calculating unit 9 that calculates
a color parameter value used for color calibration on the basis of color
parameter values at two reference color temperatures (2000 K and 3200 K),
thereby allowing performing color calibration with high color
reproducibility using suitable color parameter values according to a
change in an illumination condition as well as allowing substantially
reducing an amount of data required to determine the suitable color
parameter values.

[0051] That is, in the present embodiment, a color parameter value
corresponding to a color temperature estimated from a video signal can be
calculated with only data of color parameter values (a first color
parameter value and a second color parameter value) at two reference
color temperatures (a first color temperature 2000 K and a second color
temperature 3200 K). An amount of the data of the first color parameter
value and the second color parameter value is much smaller than an amount
of data required for conventional color parameter calibration. This
allows performing color calibration with high color reproducibility using
suitable color parameter values according to a change in an illumination
condition as well as allows substantially reducing an amount of data
required to determine the suitable color parameter values.

[0052] Further, in the present embodiment, when color calibration is
performed using the color parameter value calculated in accordance with a
change in an illumination condition, a color parameter value is
controlled so as to be gradually (e.g., slowly in about five seconds)
changed from a color parameter value corresponding to a standard color
temperature. This prevents sharp color calibration from occurring when an
illumination condition is changed, and color calibration (color
calibration using suitable color parameter values) is performed naturally
and gradually.

[0053] Further, in the present embodiment, if a captured image includes a
moving object, a color temperature may be erroneously estimated, but in
such a case, a color parameter value is controlled so that color
calibration is performed using a color parameter value corresponding to a
standard color temperature. This allows preventing color calibration
using a color parameter value calculated on the basis of an erroneously
estimated color temperature (an unsuitable color parameter value).

[0054] For example, when a person is passing in front of a whiteboard in
video, a white area might be erroneously detected. As a result, a color
temperature might be erroneously estimated. Therefore, in such a case, a
color parameter value is controlled so that color calibration is
performed using a color parameter value corresponding to a standard color
temperature. This can improve the accuracy of color temperature
estimation.

[0055] Further, in the present embodiment, if a degree of relationship
between a color temperature estimated from a video signal and a current
time is low, a color temperature may be erroneously estimated, but in
such a case, it is determined that the calculated color parameter value
is not used for the color calibration (i.e., the color calibration is
performed using a color parameter value corresponding to a standard color
temperature). This allows preventing color calibration using a color
parameter value calculated on the basis of an erroneously estimated color
temperature (an unsuitable color parameter value).

[0056] For example, in the case where an estimated color temperature is
"orange," if a current time is "morning" or "daytime," it is determined
that a degree of relationship between the color temperature and the
current time is low. On the other hand, if the current time is "evening,"
it is determined that a degree of relationship between the color
temperature and the current time is high. This can improve the accuracy
of color temperature estimation.

[0057] The embodiment of the present invention has been illustrated, but
the scope of the present invention is not limited to these examples. The
scope of the present invention can be changed and modified within the
scope of the claims to attain a particular purpose.

[0058] The foregoing has outlined a preferable embodiment of the present
invention at the present time, but it will be appreciated that the
present embodiment may be variously modified, and the appended claims are
intended to include all the modifications within the true spirit and
scope of the present invention.

INDUSTRIAL APPLICABILITY

[0059] As described above, advantageously, the camera device according to
the present invention can perform color calibration with high color
reproducibility using suitable color parameter values according to a
change in an illumination condition and can substantially reduce an
amount of data required to determine the suitable color parameter values;
the camera device is used as a surveillance camera and the like, and is
useful.